#include <iostream>
#include <cstring>
#include <stdio.h>
#include <string>
#include <cstdlib>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#define N 2
#define NUM 1024
using namespace std;

void Writer(int wfd)
{
    string s = "hello, I am child";
    pid_t self = getpid();
    int number = 0;
    char buffer[NUM];
    while (true)
    {
        sleep(1);
        // 构建发送字符串
        buffer[0] = 0; // 字符串清空，
        snprintf(buffer, sizeof(buffer), "%s-%d-%d", s.c_str(), self, number++);
        //cout << buffer << endl;
        // 发送/写入给父进程  system call
        write(wfd, buffer, strlen(buffer));
        // char c = 'c';
        // write(wfd, &c, 1);
        // number++;
        // cout << number << endl;
        // if (number >= 5) break;
    }
}

void Reader(int rfd)
{
    char buffer[NUM];
    int cnt = 0;
    while (true)
    {
        buffer[0] = 0;
        ssize_t n = read(rfd, buffer, sizeof(buffer)); // sizeof != strlen
        if (n > 0)
        {
            buffer[n] = 0;
            cout << "father get a message[" << getpid() << "]#" << buffer << endl;
        }
        else if (n == 0)
        {
            printf("father read file done!\n");
            break;
        } 
        else break;

        cnt++;
        if (cnt > 5) break;

        // sleep(3);
        // cout << "n: " << n << endl;
    }
}

int main()
{
    int pipefd[N] = {0};
    int n = pipe(pipefd);
    if (n < 0) return 1;

    // cout << "pipefd[0]: " << pipefd[0] << " , pipefd[1]: " << pipefd[1] << endl;

    // child->w   father->r
    pid_t id = fork();
    if (id < 0) return 2;
    else if (id == 0)
    {
        // child
        close(pipefd[0]); 
        // IPC code
        Writer(pipefd[1]);
        close(pipefd[1]); 
        exit(0);
    }
    // father
    close(pipefd[1]); 
    // IPC code
    Reader(pipefd[0]); // 读5秒
    close(pipefd[0]); 
    cout << "father close read fd " << pipefd[0] << endl;
    sleep(5); // 为了观察僵尸

    int status = 0;
    pid_t rid = waitpid(id, &status, 0);
    if (rid < 0) return 3;
    
    cout << "wait child success: " << rid << " exit code: " << ((status>>8) & 0xff) << " exit signal: " << (status&0x7f) << endl; 
    sleep(5);
    cout << "father quit" << endl;
    return 0;
}